Proper deformation of body mesh?
Standard skinning approaches (e.g. the armature modifier) do not support collision behavior. 

Self collision handling can be a bit tricky and certainly computationally intensive.

In blender you have two real options:


using physics simulations (cloth or softbody) which are difficult to
get right and slow to run (using a corrective smooth modifier after
the simulation can help a bit with looks though). They also don't
handle volume properly.
Manually creating corrective shapes for the intersecting poses (and potentially adding appropriate drivers if you are animating). This can be quite time consuming if you have a lot of poses you care about and want to drive everything for animation.